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Transactions of the American Mathematical Society

Published by the American Mathematical Society since 1900, Transactions of the American Mathematical Society is devoted to longer research articles in all areas of pure and applied mathematics.

ISSN 1088-6850 (online) ISSN 0002-9947 (print)

The 2024 MCQ for Transactions of the American Mathematical Society is 1.48 .

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Dimension constraints in some problems involving intermediate curvature
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by Kai Xu;
Trans. Amer. Math. Soc. 378 (2025), 2091-2112
DOI: https://doi.org/10.1090/tran/9332
Published electronically: November 19, 2024

Abstract:

In [Comm. Pure Appl. Math. 77 (2024), pp. 441–456] Brendle-Hirsch-Johne proved that $T^m\times S^{n-m}$ does not admit metrics with positive $m$-intermediate curvature when $n\leq 7$. Chu-Kwong-Lee showed in [Math. Res. Lett., to appear] a corresponding rigidity statement when $n\leq 5$. In this paper, we show sharpness of the dimension constraints by giving concrete counterexamples in $n\geq 7$ and extending the rigidity result to $n=6$. Concerning uniformly positive intermediate curvature, we show that simply-connected manifolds with dimension $\leq 5$ and bi-Ricci curvature $\geq 1$ have finite Urysohn 1-width. Counterexamples are constructed in dimension $\geq 6$.
References
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Bibliographic Information
  • Kai Xu
  • Affiliation: Department of Mathematics, Duke University, Durham, North Carolina 27708
  • Email: kx35@math.duke.edu
  • Received by editor(s): March 27, 2024
  • Received by editor(s) in revised form: September 20, 2024
  • Published electronically: November 19, 2024
  • © Copyright 2024 American Mathematical Society
  • Journal: Trans. Amer. Math. Soc. 378 (2025), 2091-2112
  • MSC (2020): Primary 53C21; Secondary 53C42
  • DOI: https://doi.org/10.1090/tran/9332